In supercritical fluid chromatography, a liquid co-solvent is mixed with a supercritical gas, such as CO2, to vary its strength as a solvent. However, the use of a high pressure system leads to undesired aerosolization of the co-solvent during collection of fractions of the eluting mixed gas liquid solvent stream. This aerosolization causes cross-contamination when attempting to collect separated compounds using a single fraction collection device for depressurization from a continuous stream. Prior art collection systems for supercritical fluid chromatography managed this problem by providing collection systems in which the collection vessels are maintained under high pressure. See, for example, U.S. Pat. Nos. 6,632,353; 6,685,828; 6,413,428; and 6,656,354, each incorporated by reference in its entirety.
It would be desirable to have a collection system which substantially reduces the aerosolization problem by avoiding cross-contamination between fractions from a single continuous stream that are separated by minimal retention time and is operable at atmospheric or near atmospheric pressure. The desired collection system would also eliminate the limitation on number of fractions that can be collected.